title: Frequent callers to and users of emergency medical systems: a systematic review.
abstract: BACKGROUND
  There appears to be a paucity of studies examining the characteristics and impact of frequent users upon emergency medical services (EMS).
  
  
  OBJECTIVE
  To review current primary research on frequent users of EMS and to identify possible gaps in the literature.
  
  
  METHODS
  Ovid, PubMed and CINAHL/Medline were systematically searched for articles that were published in English and either referred to frequent callers to or users of an EMS, or referred to frequent users of other services where admissions were via ambulance. Studies were included regardless of quality.
  
  
  RESULTS
  Eighteen studies were included. Ten were emergency department based, seven in EMS and one in a psychiatric emergency service. In emergency department studies, frequent users were more likely to arrive via ambulance than infrequent users. In EMS studies, between 0.2% and 23% of patients using EMS were frequent users accounting for 1.4% to 40% of all ambulance use. No two EMS studies used the same definition of a frequent user. No studies focused on characteristics of callers to EMS. Two studies explored interventions for frequent callers to EMS, with mixed results in reducing ambulance use.
  
  
  CONCLUSIONS
  It is unknown to what extent frequent callers impact upon EMS resources. Research should identify predictors and characteristics of frequent users of EMS, and a consistent definition of a frequent caller to or user of EMS would provide greater comparability. The lack of studies identified in this review suggests that further research is needed in order to inform policy and practice.
authors.affiliation: Faculty of Health and Life Sciences, York St John University, York, UK.
authors.forename: Jason
authors.initials: J
authors.lastname: Scott
authors.affiliation: Yorkshire Ambulance Service NHS Trust, Wakefield, UK.
authors.forename: Annette Patricia
authors.initials: AP
authors.lastname: Strickland
authors.affiliation: Yorkshire Ambulance Service NHS Trust, Wakefield, UK.
authors.forename: Karen
authors.initials: K
authors.lastname: Warner
authors.affiliation: Faculty of Health and Life Sciences, York St John University, York, UK.
authors.forename: Pamela
authors.initials: P
authors.lastname: Dawson
mesh_terms: D000367:Age Factors; D000552:Ambulances / Q000706:statistics & numerical data; D004632:Emergency Medical Services / Q000706:statistics & numerical data*; D006801:Humans; D012737:Sex Factors; D012959:Socioeconomic Factors; D013997:Time Factors
keywords: Emergency Ambulance Systems; Pre-Hospital